Need suggestions - overwhelmed by choice

My family and I are going to be visiting SF (staying near Union Sq) for a few days later this month. I'm looking for options that are:

1) Reasonably priced. I don't need bargains (but always appreciate them) and am cool with entree prices $20-35.2) I have two boys (9 and 14) with big appetites but very adventurous palates (they eat Sushi, Ethiopean, Indian, Korean food, etc.). So ethnic is great, but portions should be decent sized.3) We're only in town for a precious few days, so I'd love suggestions that aren't too much of a hike from where we're staying.4) Would also like a good Dim Sum suggestion.

For tasty, reasonably priced dim sum near Union Square, try Great Eastern in Chinatown. Yank Sing would be my number one suggestion except you say your boys have "big appetites" in which case this may turn out to be one expensive meal:-)